Cookie cannot be read by script

I'm trying to read a cookie from a browser by the following Javascript code using the js-cookie package. However, the cookie is not being read.

import Cookies from 'js-cookie';
var cookie_name = 'cookie';
var cookie = Cookies.get(cookie_name);
console.log(cookie);

The cookie is created using the below Python code that utilizes Flask.

response.headers.add('Access-Control-Allow-Headers', 'Content-Type, text/plain')
response.headers.add('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS')
response.headers.add('Access-Control-Allow-Credentials', 'true')
response.set_cookie(key='cookie',
                value=payload,
                domain='<url>')

The Flask app has the following parameters

app = Flask(__name__)
app.config['DEBUG'] = True
app.config['SESSION_COOKIE_HTTPONLY'] = False

Above I've turned off the HttpOnly flag so my script should be able to read the cookie. I also cannot see the cookie using console.log(document.cookie) in the browser. Is there any reason why my JS code can't read the cookie?

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